Many activities of the human body involve the contraction of muscles. For instance, movement of the limbs, breathing activity, etc. The most complex and vital muscular activity of the human body is that of the heart, which functions as a pump and which, by contracting at the required times and in the required manner, controls the flow of blood throughout the body.
The heart is composed of different parts, which contract differently and with different timing, in order to permit the aforementioned pumping activity. The contraction of the heart is controlled by electric stimuli, which are generated at the cellular level by chemical reaction. However, it is well known in the art to control such activity, i.e., the timing of the contraction of the cardiac muscle, by the action of externally applied electric stimuli, through the so-called “pace maker”.
In a copending PCT patent application No. PCT/IL97/00012, filed Jan. 8, 1997, the specification of which is incorporated herein by reference, of which the inventors herein are also inventors, there is described a method and apparatus for modifying the force contraction of at least a portion of a heart chamber, which comprises applying a non-excitatory electric field, for a predetermined period of time, at a delay after activation.
In the aforesaid PCT patent application No. PCT/IL97/00012 and in another copending PCT/IL patent application of the same applicants herein, filed on the same day as the present application, entitled “Apparatus and Method for Controlling the Contractility of Muscles”, and identified as the specification of which is incorporated herein by reference, there is described a method and apparatus for decreasing the force contraction of at least a portion of a heart chamber, which comprises applying a non-excitatory electric field, for a predetermined period of time, at a delay after activation. The ability to reduce the contractility is of importance in a variety of situations, e.g., during surgery or as an aid in healing of hibernated areas of a heart after myocardial infarct.
The mechanical activity of excitable cells is directly connected to their electric activity. This is most evident in the activity of the heart, which has a relatively complex electric functioning which is responsible for pacing, contraction of various areas of the cardiac muscle, as well as to the organized consecutive or simultaneous contraction of various zones. Any disturbance in the electric function of the cells may severely affect, or even stop mechanical activities of the cell. Conduction problems are also related to a variety of congenital and acquired diseases. A detailed discussion of such phenomena can be found, e.g., in the book by Donald M. Bers, “Excitation-Contraction Coupling and Cardiac Contractile Force”, Kluwer Academic Publishers, Dordrecut, Boston, London, 1993.
Treatment of electrical cellular malfunctioning is mainly confined to systemic treatment, such as by drugs or, in some cases with heart diseases, a pace maker may be required. Localized treatment, such as local ablation, is also sometime attempted. However, there are several conditions that cannot be treated by localized treatment, unless the activity of the relevant muscle is totally blocked for a suitable period of time, in a reversible manner. One example of such a condition is ventricular fibrillation or ventricular tachycardia arrhythmias, which can be induced by abnormal activity localized in a susceptible area.
Another important tool in heart therapy is the use of defibrillators. Defibrillation is a process in which an electronic device helps reestablish normal contraction rhythms in a heart that is not functioning properly, by delivering an electric shock to the heart. Defibrillators can be external or internal (implanted or inserted). Typically, a defibrillator is designed to automatically detect episodes of bradycardia, ventricular tachycardia (VT), fast ventricular tachycardia (FVT), and ventricular fibrillation (VF). When an arrhythmia is detected, the device will deliver the programmed pacing, cardioversion or defibrillation therapy. The device typically has two electrodes which are implanted. The defibrillator, as said, stops arrhythmia by delivering an electric shock, which is a painful and harmful treatment, particularly if repeated often and, importantly, it is not a localized treatment, but rather it is applied to the whole cardiac muscle.
It has now been surprisingly found, and this is an object of the present invention, that it is possible to block the activity of a localized area of cells, such as a muscle (i.e., to carry out a “fencing”), in a reversible manner, and thus to block the cell's activity for a desired period of time.
It is an object of the invention to provide apparatus for carrying out the fencing of a desired tissue area having electric activity and thereby temporarily and reversibly blocking the activity of said area.
It is another object of the invention to provide a method for treating a patient suffering from a condition treatable by temporarily blocking the electric activity of a tissue.
It is yet another object of the invention to provide a method and apparatus useful in therapy, which can be exploited in treating a variety of conditions, such as epilepsy, arrhythmia, stooping ticks, and shockless defibrillation.
Other objects and advantages of the invention will become apparent as the description proceeds.